1. Field of the Invention
The present invention relates to a mechanical loom including a shuttle for a weft thread, wherein the shuttle is shootable into the shed by means of a shooting device. The loom further includes a return device for the shuttle and a transfer device for transferring a weft thread to the shuttle.
2. Description of the Prior Art
Mechanical looms of the above-described type are known, for example, from Hollstein, Fertigungstechnik Weberei [Manufacturing Technology Weaving], Vol. 2, Mechanismen [Mechanisms], VEB Fachbuchverlag Leipzig, 1980, pages 143 to 190. Mechanical looms can be equipped either with bobbin shuttles or gripper shuttles.
In mechanical looms having bobbin shuttles, these shuttles include a bobbin with a supply of weft thread and, after each change of the shed of the warp thread, are alternatingly shot through the open shed from one or the other side of the fabric. The shooting devices are picking devices arranged on both sides of the shed. Since the bobbin shuttles must have a substantial supply of bobbins, these shuttles are relatively large and of great weight, so that the weaving speed, and thus, the output of the loom can only be relatively small. In addition, the bobbin shuttles can only receive a limited supply of thread, so that they must be exchanged within a short period of time against shuttles with full bobbins. Consequently, it is difficult to obtain patterns, i.e., to introduce weft threads of a different type or different color. Looms with bobbin shuttles are relatively expensive and cumbersome.
Some of the above-described disadvantages are avoided in gripper shuttles in which the shuttles do not have bobbins but gripping devices for a portion of the weft thread to be pulled through the shed. In mechanical looms with gripper shuttles, these shuttles are shot through the shed by means of a shooting device from only one side of the shed and pull a corresponding portion of the weft thread into the shed. A return device is required for returning the gripper shuttle or shuttles from the other side of the shed back to the shooting side. This requires complicated transport devices which return the gripper shuttle underneath the fabric web to the shooting side. During the travel through the shed, the gripper shuttles are usually guided on the weaving reed by means of guide devices, such as, guide lamella.
In mechanical looms of this type, it is a disadvantage that a plurality of gripper shuttles are required which must be returned by means of a complicated return device from the other side of the fabric web to the shooting side. In addition, the gripper shuttles must have a relatively large mass, so that a shooting device constructed as a picking device is capable of imparting to the gripper shuttle a kinetic energy of such a magnitude that it is capable of pulling the weft thread through the shed. Compared to the above-described looms with bobbin shuttles, the gripper shuttles have an improved output, however, the output is still limited and the loom is of relatively complicated construction.
Further improvements in mechanical looms are obtained if grippers are used which are moved in a positively guided manner. In these mechanical looms the grippers are pushed or pulled through the shed by means of rods or flexible belts. In unilateral grippers, the weft thread is introduced from only one side by either pushing or pulling the weft thread during the forward and backward motion by means of mechanically driven tension elements or compression elements. In two-sided grippers, a weft thread is introduced from one side of the shed into the middle thereof and is then taken over by a gripper introduced from the other side and is pulled out of the shed by means of this other gripper. If the gripper is mounted on rods, the mechanical loom requires a large installation space due to the length of the rods. In addition, due to the large masses of the rods to be moved, the weaving speeds are limited. By mounting the grippers on flexible steel or plastic belts, the mass of gripper and belt can be reduced and the structural size at the side of the mechanical loom can also be reduced, however, the wind-up devices for the belt require drive elements which are of great volume and weight, so that such a mechanical loom is still cumbersome and complicated and the efficiency and flexibility are limited. Since the grippers are moved in a positively guided manner, the times for introducing and removing them are fixed within narrow limits, so that unfavorable weft introducing conditions exist.
It is, therefore, the primary object of the present invention to improve a mechanical loom of the above-described type in such a way that the loom is of simpler construction while facilitating improved efficiency.